1. Field of the Invention
The present invention relates to a fuse and more particularly to a fuse assembly of a type having a casing made of insulating material, sockets into which tab terminals are inserted, and a fuse element constituted by a thin metal plate which has a narrower width at its midway portion and which is curved to form a U-shape, thus being attachable to the tab terminals.
2. Description of the Prior Art
Generally, the type of fuse which has been used for automobiles and the like has a narrower width portion and has a gentle characteristic, namely, a slow-blow characteristic, so that it does not cut off an excessive current or a lock current flowing for a short time at a level higher than the steady current value but is safely fused by an excessive current flowing at a level higher than the steady current value for a long time, for example, by a a short-circuit current. Such a slow-blow fuse is disclosed in Japanese Utility Model Publication No. 41563 / 1984, in which tab sockets into which tab terminals are inserted are integrally formed at the opposite ends of a fuse element.
For the purpose of integrally forming the tab terminal sockets at the opposite ends of the fuse element, it is necessary to use an electrically conductive material having a a, for example, copper alloys having high fusion points such as phosphor bronze, etc. If the fuse portion is made of phosphor bronze, it does not fuse when the temperature thereof is under 1000.degree. C., and the resilience of the socket is reduced by heat conduction before the temperature of the fuse portion reaches that level, so that the contact resistance between the socket and a tab terminal is increased and the socket is thereby heated even more. The resilience of the socket is then reduced further, and the heat thereof is again increased. Thus there is a fear of combustion of the casing before the fuse portion is actually blown through such a recurring process. Moreover, it is uneconomical for the entire fuse including its socket terminal portions or the whole of the fuse assembly to have to be replaced when the fuse element is blown.